Correct me if I'm wrong, but doesn't material stiffness play a direct role in flutter? I understand that natural resonance frequencies of a structure are determined in part by material stiffness (the stiffer the material the higher the frequency). Wouldn't the natural resonance frequency of a composite structure change with a partial delamination of the composite material in that structure?
Regarding the accident aircraft, I'm curious as to what caused the delamination of the tail fin mounting point while the aircraft was still on the factory floor. Was it caused by an accidental collision with some other object in the factory during assembly, or was it a resin mixture problem, or maybe an incorrect heating profile in the autoclave?
An impact delamination would not have the same long term consequences that a materials processing error would. A materials processing error, that might cause more widespread delamination over time, would certainly alter the natural frequency and therefore the flutter characteristics of an aircraft structure. Any loss in stiffness in any of the fin attachment points would seem to have a direct bearing on the natural frequency of the fin/fuselage join.
(Edited for a spelling error, and adding an extra comment)
[ 18 November 2001: Message edited by: Flight Safety ]